1. Field of the Invention
A heating or air conditioning unit for a motor vehicle having a plurality of independent temperature control regions.
2. Description of Related Art
U.S. Pat. No. 4,482,009 discloses a conventional heating or air conditioning unit, including a fan and a heater, which divides the airstream downstream of the heater. Two ducts leading to the vehicle front compartment distribute conditioned air to the regions for the driver seat and passenger seat, and two ducts leading to the vehicle rear compartment distribute conditioned air to the regions for the seat behind the driver and the seat behind the passenger. Air control elements arranged at the branching points of the air ducts control the quantity of air supplied to each region; however, independent temperature control is only possible between the front and rear zones. Additional air control elements provided further downstream allow the air stream to the front zone to mix with the air stream to the rear zone; however, temperature control is still dependent on the position of the air quantity control elements for the other regions.
DE-A 39 40 361 discloses another conventional heating or air conditioning unit providing conditioned air to the rear zone of a motor vehicle. A first air duct conducts cold air and a second air duct conducts hot air. Air from the first and second ducts is combined in a mixing chamber so as to set the desired temperature of the air stream that goes to the rear zone. One disadvantage of this conventional arrangement is a duct conducting conditioned air to the foot region of the rear zone branches off from the hot air duct upstream of the mixing chamber, hence its temperature is dependent on the temperature setting in the front zone. Another disadvantage is the considerable amount of space required in the rear zone to control the amount of air to the rear zone.